SDN: Where is it now and what is the future?

Software-defined networking is one of the great IT hype stories of this century – we look at where it stands now

It is well documented that initial uncertainty over exactly what software-defined networking (SDN) was, meant that initial uptake was slower than had been hoped. This point was emphasised by the reality that, in the early days, getting two similar definitions of SDN from any two suppliers or analysts was a major challenge.

In 2011, the Open Networking Foundation (ONF) essentially popularised the concept as an open source architecture, its definition being similar to that of Gartner at the time: “Emerging networking architectures that separate the control plane from the data plane in networking equipment, so that network intelligence and state are logically centralised, and the underlying network infrastructure is abstracted from applications.”

Significant role in the datacentre

Chris Dando, chief technologist at HPE in Europe, the Middle East and Africa (Emea), says there is a significant role for SDN in the datacentre, especially in industries such as media and entertainment. “What many people didn’t realise is how the network fabric in the datacentre needed to change, as we saw the advent of collapsed storage and applications,” he says. “So we are seeing the adoption of software-defined storage as we move more towards a software-defined, cloud-native environment.”

Regardless of the absolute definition, one key element was that networks could be directly programmable from end to end, rather than on a “per hop” basis, between routers, and that they could be managed centrally. In other words, the network – from an applications and user policy perspective – became a single, logical switch, rather than a series of inter-nodal routes. This approach was initially followed by many of the big guns in the networking industry, although often with a more proprietary, or at least “personalised” approach, such as Cisco’s Open Network Environment (ONE).

SDN also spawned a plethora of startups, but a quick analysis of those startups from around 2011-2013 shows many of them have since been acquired, for example:

So has this resulted in a change of direction or definition for SDN? Mike Capuano, CMO of Pluribus, one of the early SDN startups that has remained independent, says: “At Pluribus we have worked hard to learn from the latency, resiliency and brownfield insertion pitfalls of first generation SDN based on external controllers and OpenFlow. We define Next Generation SDN as a controllerless solution where the intelligence of the SDN controller is distributed throughout the network.”.

Capuano believes integration and interoperability have been key. For example, in Pluribus’ case, aggregation with the likes of Dell, and Layer 2-3 interoperability with leading networking suppliers such as Cisco, Juniper and Arista, notably in the formation of “spine and leaf” architectures. He sees the advent of cloud as also having changed the role of SDN, such as in the form of an adaptive, controllerless cloud fabric. “Having fixed controllers talking out of band to a switch is not optimal,” he says. “If a link fails between them, it means you can’t program the switch they are controlling.”

The argument follows that if an IT architecture dictates the need for data to be sent to a specific network controller, then latency becomes an issue. The alternative definition by Pluribus is of globally deployed networks, with in-band management, where the controller lives within the network switches and the network fabric interconnects at the management plane, effectively acting like one big switch. This means any switch can be a controller. As such, there is no single point of failure.

This is much in keeping with the original concept of SDN. One of the issues from day one, however, was: who was it aimed at? Despite the technology now having been around for several years, Capuano believes the market is still maturing and hardening, particularly on the enterprise side, which currently forms about 50% of Pluribus’ user base. Within those enterprise customers, Capuano sees integration with VMware as a key element.

Read more about next generation networking

Suppliers are pushing the benefits of software-defined networking harder than ever, and enterprises are starting to take the plunge rather than remaining on the sidelines.

Take-up of software-defined networking in corporates is slower than expected. Where have we reached on the journey to software-controlled networks – and SD-WAN in particular – becoming the norm?

A recent Gartner report implied that SDN has very much been a catalyst of change, rather than being directly adopted by the enterprise. Gartner distinguished analyst Joe Skorupa says: “SDN started as a new technical architecture, but brought to light some valuable concepts that outlived the original blueprint.”

The limited adoption of enterprise SDN noted by Gartner is put down to the conservative nature of networking buyers, a lack of immediate business drivers, and the market power of incumbent network equipment providers. But Gartner reports a different story in the service provider market, where it sees OpenFlow becoming synonymous with SDN, and gaining significant traction.

Forrester principal analyst Andre Kindness says there has also been a change in the application of SDN, driven by interactions with the public cloud, connections to branch office and the impact of the internet of things (IoT).

Tying in with these analyst views, a number of more recent SDN-related startups have been spawned, taking the technology in related, but different directions. One example is NetFoundry, described by its head of Emea partnerships, Philip Griffiths, as “a software-defined networking solution that is designed to transform the way the world connects to applications and data”.

The company has created the concept of AppWANs – private, application-specific networks that create a secure, optimised overlay network on top of the public internet. “It’s 100% software, so we can pin up a global private network in minutes, just like spinning up servers in the cloud,” says Griffiths.

That also defines NetFoundry’s security approach. The technology has a software-defined perimeter (SDP), which means its network endpoints are invisible to the network, do not respond to requests, have no inbound ports open, and obfuscate IP address and software firewalls with just one rule – deny all inbound traffic. Network connectivity is made outbound only when authenticated and driven by the customer’s dedicated network controller.

Todd Krautkremer, CMO of Cradlepoint, believes the concept of an SDP should be extended into the world of IoT. “With IoT, devices are connecting directly, not in the form of a subnet-type network, so there’s the notion of software-defined perimeter – how do I connect a device to a cloud app?” he says.

Cradlepoint is an example of taking an SDN startup and evolving it to fit the changing architectural landscape in the shape of Pertino, acquired by Cradlepoint back in 2015. Krautkremer views SDN as an architecture, not a technology, and a means to bring customers from the network to the cloud.

The company is also heavily involved in the transition of wired to wireless, through LTE to 5G and sees SDN and SD-WAN extending over 5G to the likes of in-vehicle management and emergency services, citing the endpoint management capabilities as of primary interest, for example in retail.

“A company such as Boots has expanded through acquisition, meaning more stores, so more endpoints,” says Krautkremer. “Health service expansion means stores within stores. Boots is looking for SD-WAN capabilities to manage that expansion without having to grow staff count by, say, 30%.”

Meanwhile, 451 Research believes the challenge of companies such as Cradlepoint will be to build mindshare among enterprises that have already seen success among their peers in stitching together SD-WAN and branch network as a service.

“Companies with a large number of locations, such as retail chains, have been asking how they can optimise their WAN costs,” says Aruba CTO Simon Wilson.

“Historically, they have had global MPLS networks and have been beholden to one provider, which has been restrictive when they have wanted to make bandwidth changes or spin up new locations. So they are looking for a more agile, reactive alternative.”

While mainly focused on pure data scenarios, SDN has also expanded into voice. Aritari provides software-defined virtual private network software that overcomes inefficiencies found on the internet, such as packet loss and latency, to deliver domestic or global networking, providing both voice optimisation and data acceleration in a single product.

It is clear that SDN has expanded significantly beyond its original definitions. Most of those first-stage SDN companies have long since been swallowed up, either by second-stage entrants or by the major network equipment providers. So the SDN story is far from finished, and there are likely to be more twists and turns as it becomes enterprise ready.

This was last published in December 2018

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